Butyl Tape VS Silicon

Getting ready to install deck hardware, what is the pros and cons of using butyl tape over silicon ?

kartracer said:

Getting ready to install deck hardware, what is the pros and cons of using butyl tape over silicon ?

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Butyl tape is easy and works well. Silicone, once it hits anything, will keep anything else from sticking to it. Do yourself a favor and remove any silicone sealant or adhesives from the boat.

CMS has a great article on how to use butyl tape for bedding hardware. Easy to do and will last just about forever. It is also inexpensive.

I've read CMS's article on butyl tape and although I have great respect for him (we've actually met) I don't understand his stance on silicone.
Our 2005 Sabre was built with a combination of urethane, silicone and butyl tape sealers and it was fine, well mostly fine!
This is a boat that was sailed a lot. Three trips to Bermuda and back along with a trip to Maine and back every year.
Yes there were leaks. The outer T tracks mounted through the teak cap rails sealed with butyl tape and urethane leaked and had to be re-sealed. A couple of chocks sealed with silicone developed small leaks. The through bolts for the massive chain plates/deck sandwich leaked.
I resealed with what the factory used for the most part with the exception of the chain plates, they were bedded in 5200 with butyl tape on the thru bolts. They still leaked every few years at the bolts and I finally learned to simply replace the butyl annually.
We had tons of green water on that deck and had very few problems with leaks from silicone sealed hardware.
Silicone wouldn't be my first choice but it was easy to work on and it was reliable enough...
When I mount hardware I always bevel the hole to leave space for sealant when tightened and I typically go to urethane type sealers. I particularly like 3M 4000 uv as it doesn't degrade in the sun so it maintains a nice edge and it comes apart reasonably.
I believe that the type of sealant is less important than the prep of the pieces to be joined actually...
Bruce

"When I mount hardware I always bevel the hole to leave space for sealant when tightened"

Some folks bevel and slip on an O ring for a pressure seal.

We had a sailboat that had the worst caulk job I've ever seen. Chasing leaks, the PO had simply squirted a bead of silicone around the exterior seams of every fitting on deck and around the entire perimeter of the deck where it abutted the toe rail. And despite what he must have thought was an impenetrable water barrier, it still leaked. A child would have known better.

It took a long to get the bulk of it off and the surfaces never were entirely free of a greasy film that prevented anything from adhering to the fiberglass. Ultimately, I ripped everything off the boat above the waterline--including the teak toe rail and vinyl rub rail--and rebedded properly with Sikaflex. If I'd known about butyl tape back then, I'd have used it; all of the above-water-line fittings on the Defever are getting butyl.

To me, the choice between silicone and butyl for bedding fittings is the same as choosing between brandy or diesel for an after dinner drink.

I'd use burly tape #1
Many others #2 - ...?
Silicone would be my last resort.
I and many others don't keep it on my Boat.
I hear there is a wide variety in butyl tapes and worth buying good stuff (CMS sells what some consider the best)
I don't believe builders always do what's best long term...rather what works short term...some don't install proper backing...otbers leave coding exposed when drilling..etc...etc

angus99 said:

We had a sailboat that had the worst caulk job I've ever seen. Chasing leaks, the PO had simply squirted a bead of silicone around the exterior seams of every fitting on deck and around the entire perimeter of the deck where it abutted the toe rail. And despite what he must have thought was an impenetrable water barrier, it still leaked. A child would have known better.

It took a long to get the bulk of it off and the surfaces never were entirely free of a greasy film that prevented anything from adhering to the fiberglass. Ultimately, I ripped everything off the boat above the waterline--including the teak toe rail and vinyl rub rail--and rebedded properly with Sikaflex. If I'd known about butyl tape back then, I'd have used it; all of the above-water-line fittings on the Defever are getting butyl.

To me, the choice between silicone and butyl for bedding fittings is the same as choosing between brandy or diesel for an after dinner drink.

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Your point is actually the same as mine with a different conclusion. It is the prep not the caulk that makes the job. I'm sure that if the person who squeezed silicone all over the boat had chosen 5200 or butyl, the result would have been exactly the same.
Bruce

Greetings,
Mr. k. ANYTHING BUT SILICONE!!!!! Peanut butter, pureed okra, pine gum...Butyl tape, Dolfinite or 3M 4000 would be my choice.

bestmaterials has a good selection of butyl tape and good pricing...

Butyl Rubber | Butyl Rubber Tapes, Butyl Caulks, Butyl Sealants

I've read enough Of TF threads to know that when I bought my boat, I bought butyl tape as I was afraid NOT to have any AND I bought Compass Marines particular brand as most people said it was the best and superior to all others

No silicone for me. Been there, did that, regretted it. uv4000, 4200, 5200, or butyl tape for me, but I do wonder how long pureed okra holds up?

Bruce B said:

Your point is actually the same as mine with a different conclusion. It is the prep not the caulk that makes the job. I'm sure that if the person who squeezed silicone all over the boat had chosen 5200 or butyl, the result would have been exactly the same.
Bruce

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While inept prep was clearly a problem in my example, I would not use silicone anywhere on my boat. If I had to rebed a fitting bedded with silicone, I'd be stuck with using silicone again (or potentially not stuck being the bigger issue).

angus99 said:

While inept prep was clearly a problem in my example, I would not use silicone anywhere on my boat. If I had to rebed a fitting bedded with silicone, I'd be stuck with using silicone again (or potentially not stuck being the bigger issue).

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Again,
Prep is everything! I've successfully re-bedded hardware that was originally installed with silicone with other caulks.
Not sure why I argue these things in places like this. It gets me nowhere...
Ok, no silicone, ever, ever, ever.
There!
Bruce

Bruce B said:

Again,
Prep is everything! I've successfully re-bedded hardware that was originally installed with silicone with other caulks.
Not sure why I argue these things in places like this. It gets me nowhere...
Ok, no silicone, ever, ever, ever.
There!
Bruce

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Certainly not asking you to agree. It's your boat . . .

angus99 said:

Certainly not asking you to agree. It's your boat . . .

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Right, the boat...
A 2005 Sabre 386, carbon rig, deep draft set up for complying with Newport to Bermuda race rules.
Purchased new, most deck hardware sealed at the factory with silicone, used hard with multiple Gulf Stresm crossings (lots of green water on deck for days sometimes!) and (mostly) without leaks except in places where butyl tape was used... those places being the genoa T track bolts that the factory wrapped with butyl tape and the chain plates clamp bolts that were also wrapped with butyl tape by the factory. The only failure of a silicone sealed deck hardware piece was a chock that showed signs of rust on a fastener after a few years use. I removed it, rebedded it with 3M 4000 and never had a problem again.
All the rest of the deck hardware, tracks, blocks, hatches and stanchions are still not leaking after 11 seasons of use even though they were bedded with silicone.
Bad silicone!
Bruce

Bruce B said:

When I mount hardware I always bevel the hole to leave space for sealant

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I would consider this a 'best practice' because it also reduces the chances of cracking gelcoat. Once the gelcoat cracks, it can act like a crack in windshield and start 'running'. The same reason why you would want to radius all corners when cutting.

Shrew said:

I would consider this a 'best practice' because it also reduces the chances of cracking gelcoat. Once the gelcoat cracks, it can act like a crack in windshield and start 'running'. The same reason why you would want to radius all corners when cutting.

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My other favorite practice in mounting hardware is to tap threads into the actual fiberglass piece the hardware is bedded to. I read of this practice used by Hinckley in one of Ference Maté's books and it seemed like a good technique.
I still bevel the hole afterward and of course as always use a good backing plate.
Never had a leak when I used that little trick...
Bruce

Butyl tape gets my vote! stays gooey for years. seals well yet the pieces come apart once the fasteners are removed. It is easy to store and lasts years in its paper wrapping ready to apply without drying out. As has been previously posted a light countersink is a good idea.

angus99 said:

While inept prep was clearly a problem in my example, I would not use silicone anywhere on my boat. If I had to rebed a fitting bedded with silicone, I'd be stuck with using silicone again (or potentially not stuck being the bigger issue).

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Even silicone won't stick to silicone without chemical or mechanical removal...If you go through the work of prep I'd use anything else the rod time...Well maybe not okra???

Anything but silicone is my choice. I won't use silicone except if I must reseal old silicone

Bacchus said:

Even silicone won't stick to silicone without chemical or mechanical removal...If you go through the work of prep I'd use anything else the rod time...Well maybe not okra???

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Yeah, it's been a long time since I removed it, but I think I used a combination of razor blades, bronze wool, acetone and emory cloth. Basically, I removed the silicone by removing the surface of the gel coat . . . and stuff still wouldn't stick to it.

Welcome to the new anchor thread!

Buytl tape absolutely first choice. Silicone absolutely last choice. Read the process on the pbase web site. Works very well.

Butyl tape every time. I've also used it to take out the squeak of wood on fiberglass.

Is the 3M products, 4000-4200-5200 not silicon ???? 4000 is product I was thinking of using.

kartracer said:

Is the 3M products, 4000-4200-5200 not silicon ???? 4000 is product I was thinking of using.

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Yes, none of those are silicone. 4000 is about the same strength as 4200. 4200 and 5200 are polyurethanes and 4000 is a polyether. All 3 are listed for use above and below the waterline. 4000 cures typically in 24hrs and stays white much better than 4200 or 5200 when exposed to the sun for long periods. Since it works about the same as 4200 but doesn't degrade in sunlight and I don't usually know ahead of time where I'm going to use some sealant, I don't even bother to buy 4200, I just buy 4000.

Ken

I had some sort of black gooey stuff that bedded my boat windows. Everytime someone leaned against the joint, they would have a black, hard to clean strip on their shirt. The stuff kept migrating out of the joint, years later. It would dissolve in mineral spirits, but not water. Is that butyl tape?

Sounds like 3M weatherstrip adhesive.

OK, the only thing messier in my life has been uncured black 5200 and coal tar epoxy.

Bruce B said:

Again,
Prep is everything! I've successfully re-bedded hardware that was originally installed with silicone with other caulks.
Not sure why I argue these things in places like this. It gets me nowhere...
Ok, no silicone, ever, ever, ever.
There!
Bruce

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I'm with you, Bruce. When I bought my boat, the bow pulpit was liberally sealed with silicone. When redesigning and rebuilding it, I cleaned the silicone residue with MEK or acetone and a wire brush. It cleaned up well. Then I used a combination of sikaflex and butyl tape on the various surfaces to reseal the assembly.

Last year it got rebuilt again after a 60' Hatt parked on my bow pulpit on SF Bay. I had the boat yard use the same materials and it's been leak free.
For the non-skid deck-to-wood surface, I used Sikaflex. On the smooth SS plate-to-epoxy/varnish wood surface, I used butyl tape. All told, it's been leak-free for about 7 years.

Discovered the butyl tape on this forum and its use by instructions on Compass Marine has totally stopped two areas of nuisance leaks that I could never master in the past. Where I can use it first, I will.